A. Field of the Invention
The invention relates to a photo drive which can be slid into any standard PC 5.25" bay and integrated with a personal computer, especially to a document-tray-driven photo drive which can scan a transparent sheet as well as a reflective sheet.
B. Description of the Prior Art
The recent development of scanner technology can shrink the size of a flatbed scanner to the size of a conventional CD-ROM driver. The compact scanner is called "photo drive" which can be slid into any standard PC 5.25" bay and integrated with a personal computer. Due to the size restriction, the main issue for the design and manufacture of the photo drive is how to simplify its inner structure without sacrificing its functions.
Currently the photo drive available on the market is paper-driven. Refer to FIG. 1, the illuminating device 101 and photoelectric converting device 102 are both fixed. When scanning, an original sheet is slipped into the opening between the upper paper guide 103 and the lower paper guide 104. When the pulleys 105 rotate and touch the original sheet, the original sheet will be automatically guided into the housing. The process of scanning begins as soon as the original sheet is fed in. The window 106 on the lower paper guide 104 allows the light beams from the illuminating device 101 to emit through. The light beams shone on the original sheet will then be reflected to photoelectric converting device 102 via mirror 107. When the exposure is finished, the pulleys 105 will guide the original sheet out.
In addition to the complexity of its structure, the design of the paper-driven structure has several disadvantages. First, when the original sheet is guided by the pulleys 105, the surface of the original sheet is likely to be scratched by the pulleys 105. It causes paper dust to fall on the window 106 or mirror 107. The contamination on the window 106 or mirror 107 will influence the clarity of the images. Moreover, the friction factors between the pulleys 105 and the original sheet are hard to control. If the friction factors are too small, the pulleys 105 are not able to roll the original sheet into the housing. If they are too large, the pulleys 105 will scratch the surface of the original sheet and generate paper dust. Furthermore, the design of the paper guides is too complicated and not practical in application. It cannot guarantee that the original sheet will be guided smoothly into the housing. If the original sheet is not guided properly, the image of the original sheet will be screwed up.